This book mainly focuses on the investigation of the electric-field control of magnetism and spin-dependent transportation based on a Co40Fe40B20(CoFeB)/Pb(Mg1/3Nb2/3)0.7Ti0.3O3(PMN-PT) multiferroic heterostructure. Methods of characterization and analysis of the multiferroic properties with in situ electric fields are induced to detect the direct magnetoelectric (ME) coupling. A switchable and non-volatile electric field control of magnetization in CoFeB/PMN-PT(001) structures is observed at room temperature, and the mechanism of direct coupling between the ferroelectric domain and ferromagnetic film due to the combined action of 109° ferroelastic domain switching in PMN-PT and the absence of magnetocrystalline anisotropy in CoFeB is demonstrated. Moreover, the electric-field control of giant magnetoresistance is achieved in a CoFeB-based spin valve deposited on top of (011) oriented PMN-PT, which offers an avenue for implementing electric-writing and magnetic-reading random access memory at room temperature. Readers will learn the basic properties of multiferroic materials, many useful techniques related to characterizing multiferroics and the interesting ME effect in CoFeB/PMN-PT structures, which is significant for applications.

"a very detailed book on multiferroics that will be useful for PhD students and researchers interested in this emerging field of materials science" —Dr. Wilfrid Prellier, Research Director, CNRS, Caen, France Multiferroics has emerged as one of the hottest topics in solid state physics in this millennium. The coexistence of multiple ferroic/antiferroic properties makes them useful both for fundamental studies and practical applications such as revolutionary new memory technologies and next-generation spintronics devices. This book provides an historical introduction to the field, followed by a summary of recent progress in single-phase multiferroics (type-I and type-II), multiferroic composites (bulk and nano composites), and emerging areas such as domain walls and vortices. Each chapter addresses potential technological implications. There is also a section dedicated to theoretical approaches, both phenomenological and first-principles calculations.

The considerable interest in graphene and 2D materials is sparking intense research on layered materials due to their unexpected physical, electronic, chemical, and optical properties. This book will provide a comprehensive overview of the recent and state-of-the-art research progress on layered materials for energy storage and other applications. With a brief introduction to layered materials, the chapters of this book gather various fascinating topics such as electrocatalysis for fuel cells, lithium-ion batteries, sodium-ion batteries, photovoltaic devices, thermoelectric devices, supercapacitors and water splitting. Unique aspects of layered materials in these fields, including novel synthesis and functionalization methods, particular physicochemical properties and consequently enhanced performance are addressed. Challenges and perspectives for layered materials in these fields will also be presented. With contributions from key researchers, Layered Materials for Energy Storage and Conversion will be of interest to students, researchers and engineers worldwide who want a basic overview of the latest progress and future directions.

Written by well-known experts in the field, this first systematic overview of multiferroic heterostructures summarizes the latest developments, first presenting the fundamental mechanisms, including multiferroic materials synthesis, structures and mechanisms, before going on to look at device applications. The resulting text offers insight and understanding for scientists and students new to this area.

The electric field control of ferromagnetism has been a long sought after effect, due to the large number of potential applications in electronic/magnetic devices. Large currents (and hence large powers) are required to generate the large magnetic fields needed to control the magnetization of a ferromagnetic material in a thin film electronic device, which is incompatible with planar integrated circuit technology. Alternatively, creating large electric fields at these scales requires minimal current (and hence minimal power) and is already well established. By exploiting a magnetoelectric material, magnetization can be manipulated in a scalable planar low-power device through the application of electric field. Using this type of device architecture could lead to huge advances in magnetic memory and storage, as well as provide a crucial first step to creating low-power spintronic devices as a replacement for traditional electronics that are reaching the limit of scaling. One possible way to achieve the electric control of ferromagnetism is by controlling exchange bias, the shift of a magnetic hysteresis curve along the applied field axis due to interface interactions between coupled antiferromagnetic (AFM) and ferromagnetic (FM) materials. If it is possible to shift exchange bias through the coercive field of the FM, magnetization can be reversed. Reaching this goal requires a careful understanding of antiferromagnetism, ferromagnetism and the interactions between the two when coupled (exchange bias). The main focus of this thesis will be the design, fabrication, characterization, and understanding of an electric field effect device where we are able to reversibly modulate between two exchange bias states with opposite polarity in a thin film ferromagnet by coupling it to a multiferroic (ferroelectric/antiferromagnetic) material. The multiferroic material BiFeO3 (BFO), an AFM and ferroelectric (FE) with coupled AFM/FE order parameters, is a prime candidate material for affecting change in exchange bias systems. When coupled to a thin film ferromagnet such as the colossal magnetoresistive manganite La0.7Sr0.3MnO3 (LSMO), one can envision a system where FE order is switched in BFO, which induces a change in AFM order in BFO, which induces a change in exchange bias in LSMO. Here, an electric field effect device is created using BFO as the dielectric and LSMO as the conducting channel to realize just such a system. Heteroepitaxially deposited BFO (3 nm)/LSMO (200 nm) heterostructures are grown on SrTiO3 (100) substrates and subsequently patterned into field effect devices using a fabrication process involving photolithography and argon ion milling. These devices are then characterized through magnetotransport measurements to characterize the magnetic properties of the LSMO channel with respect to BFO FE polarization. Through these measurements this thesis shows, for the first time, exchange bias is directly controlled with electric field without temperature cycling or any electric or magnetic field cooling/biasing. This effect is reversible and comes concurrently with the modulation of channel resistance (sometimes over 300%), the modulation of magnetic coercivity, and magnetic Curie temperature. Based on these results and the current understanding of exchange bias we propose a model to understand the electric control of exchange bias. In this model the coupled antiferromagnetic/ferroelectric order in BFO along with the modulation of interfacial exchange interactions due to ionic displacement of Fe3+ in BFO relative to Mn3+/4+ in LSMO cause exchange bias modulation.

This dissertation presents a study of a heterostructure composed of room temperature magnetoelectric multiferroic BiFeO3 and ferromagnetic Co90Fe10, with specific interest in understanding the interfacial coupling mechanisms in this system and establishing the electric field control of a magnetization and spintronic devices. The field of spintronics has been plagued with the problem of a large energy dissipation as a consequence of the resistive losses that come during the writing of the magnetic state (i.e. reversing the magnetization direction). The primary aim of the work presented here is to investigate and understand a novel heterostructure and materials interface that can be demonstrated as a pathway to low energy spintronics. In this dissertation, I will address the specific aspects of multiferroicity, magnetoelectricity, and interface coupling that must be addressed in order to reverse a magnetization with an electric field. Furthermore, I will demonstrate the reversal of a magnetization with an electric field in single and multilayer magnetic devices. The primary advances made as a result of the work described herein are the use of epitaxial constraints to control the nanoscale domain structure of a multiferroic which is then correlated to the domain structure of the exchange coupled ferromagnet. Additionally, the magnetization direction of the ferromagnetic layer is controlled with only an applied electric field at both macroscopic and microscopic scales. Lastly, using this electric field control of ferromagnetism, the first demonstration of a magnetoelectric memory bit is presented.

FERROIC MATERIALS-BASED TECHNOLOGIES The book addresses the prospective, relevant, and original research developments in the ferroelectric, magnetic, and multiferroic fields. Ferroic materials have sparked widespread attention because they represent a broad spectrum of elementary physics and are employed in a plethora of fields, including flexible memory, enormous energy harvesting/storage, spintronic functionalities, spin caloritronics, and a large range of other multi-functional devices. With the application of new ferroic materials, strong room-temperature ferroelectricity with high saturation polarization may be established in ferroelectric materials, and magnetism with significant magnetization can be accomplished in magnetic materials. Furthermore, magnetoelectric interaction between ferroelectric and magnetic orderings is high in multiferroic materials, which could enable a wide range of innovative devices. Magnetic, ferroelectric, and multiferroic 2D materials with ultrathin characteristics above ambient temperature are often expected to enable future miniaturization of electronics beyond Moore’s law for energy-efficient nanodevices. This book addresses the prospective, relevant, and original research developments in the ferroelectric, magnetic, and multiferroic fields. Audience The book will interest materials scientists, physicists, and engineers working in ferroic and multiferroic materials.